Lumped element circulator

ABSTRACT

In a lumped element circulator wherein three line conductors are arranged on the surface of a ferrimagnetic substrate with cross angles of 120* with respect to one another and in a manner to be insulated from one another, capacitive elements are connected between the input ends of the respective line conductors and an outer conductor. Terminating parts of the respective line conductors are connected to a conductor plate provided on the back of the ferrimagnetic substrate, and a DC magnetic field is applied perpendicularly to the plane of the ferrimagnetic substrate. The lumped element circulator comprises capacitors connected in series with the respective line conductors, and a coil connected between the conductor plate and the outer conductor.

United States Patent [191 Maeda et al. Sept. 17, 1974 LUMPED ELEMENT CIRCULATDR v Prima Examiner-Paul L. Gensler 75It:M1nMdI-Ih.;lhr nven ors ss t zz g j g y Attorney, Agent, or FirmCra|g & Antonelll [73] Assignee: Hitachi, Ltd., Tokyo, Japan ABSTRACT [22] Filed: June 25, 1973 In a lumped element circulator wherein three lme con- PP 372,937 ductors are arranged on the surface of a ferrimagnetic substrate with cross angles of 120 with respect to one 52 US. Cl. 333/11 333/84 M amber and in a manner be insulated fmm 51 Int. Cl. ..H01 1/32 her, capacitive elements are nnected between 58] Field of Search 333/1.1 input ends the respective line and an outer conductor. Terminating parts of the respective [56] References Cited line conductors are connected to a conductor plate provided on the back of the ferrimagnetic substrate, UNITED STATES PATENTS and a DC magnetic field is applied perpendicularly to RObCTtS, Jl'. .t the plane of the ferrimagnetic substrate The lumped 21137 8 g h'gl element circulator comprises capacitors connected in 3 605 040 9/1971 K32: i I I A series with the respective line conductors, and a coil 31614675 10/1971 Konishi"m1::...........:::::: iiii3ll.1 k cmmected between the conduct Plate and the outer 8/l969 Japan 333/1.l

conductor.

16 Claims, 14 Drawing Figures PATENTEDSEPITIQM 3,836,874

' SHEET'I 0P3 FIG. I PRIOR ART- I "2 FIG. 2 PRIOR ART PATENTED I 71974 3.836.874

sum 2 BF 3 FIG. 5b I PAIENTEU SEP 1 7 I974 v sum 3 or 3 SATURATION MAGNETIZATION Ms=400 Gauss FIG. IO

INTERNAL DC MAGNETIC FREQUENCY. (GHz) G W L H L m m 0 R F P 0 II D. 0 E w m 3 x En l .A FH NF H T w W 0 NH B I- B d 0 F 0 O O 3 2 FIG.

FIG. II

FIG.

LUMPED ELEMENT CIRCULATOR BACKGROUND OF THE INVENTION The present invention relates to lumped element circulators and, more particularly, to a lumped element circulator which compensates for parasitic reactances.

DESCRIPTION OF THE PRIOR ART Lumped element circulators have hitherto been constructed on the basis of a structure as shown, by way of example, in FIG. 1. On the surface of a ferrimagnetic substrate 31, three line conductors 1 l-ll, 12-12 and 13-13 are formed. The respective line conductors are separated into two parallel conductor lines 21 and 22, 23 and 24, and 25 and 26, and define cross angles of 120 with respect to one another. In order to provide electrical insulation a technique such as deposition and electroplating is employed in the formation of the line conductors. The three line conductors are connected at the terminating end parts 11', 12' and 13 to a conductor plate which is provided on the back of the ferrimagmetic substrate. A DC magnetic field is applied perpendicularly to the plane of the ferrimagnetic substrate 31. Then, an equivalent circuit with the substrate side viewed from the input terminals 11, 12, and 13 is as shown in FIG. 2 and includes nonreciprocal inductive I elements 41, 42 and 43. A prior-art lumped element circulator is constructed, as shown by its equivalent circuit in FIG. 3, with suitable capacitive elements 44, 45 and 46 connected between the respective input terminals and an outer conductor. The nonreciprocal induc tive elements 41, 42 and 43 shown in FIG. 2, however, generally contain not only components contributing to the nonreciprocal operation of the circulator, but also components functioning as mere reciprocal elements. The latter components manifest themselves in the form of parasitic reactance components. As a consequence, the circuit arrangement shown in FIG. 3 is disadvantageous in that the reciprocal components cannot be compensated and sufficiently good circulator characteristics cannot be attained.

Further, it is often the case that the static coupling capacitance between the line conductors at the crossing parts and the series inductance attributable to the line conductor at each input terminal part cannot be neglected. For this reason, the circuit arrangement shown in FIG. 3 has the disadvantage that parasitic reactance components due to the coupling capacitance and the series inductance cannot be compensated, which leads to unsatisfactory circulator characteristics.

SUMMARY OF THE INVENTION An object ofthe present invention is to eliminate the disadvantages of the prior-art lumped element circulator, and to provide a lumped element circulator which compensates for parasitic reactances.

In order to accomplish the object, the present invention compensates reciprocal components contained in nonreciprocal inductive elements which conduct the circulator operation.

Also, in order to accomplish the object the present invention compensates the series inductance existing at each input part of a line conductor or the electrostatic coupling capacitance between the line conductors.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic plan view showing an example of construction of line conductors in lumped element circulators having hitherto been used;

FIG. 2 is an equivalent circuit diagram of the lumped element circuit as shown in FIG. 1;

FIG. 3 is an equivalent circuit diagram of a prior-art lumped element circulator;

FIG. 4 is an equivalent circuit diagram of an embodiment of the circulator according to the present inven- I tion;

FIGS. 5a and 5b are views of the embodiment realizing the equivalent circuit in FIG. 4;

FIGS. 6 and 7 are equivalent circuit diagrams of further embodiments of the present invention;

FIGS. 8a and Share equivalent circuit diagrams of intrinsic impedances with parasitic reactance components taken into consideration;

FIG. 9 is an equivalent circuit diagram of still a further embodiment of the circulator according to the present invention;

FIG. 10 illustrates an example of calculation of a frequency band characteristic;

FIG. 11 is a view showing the embodiment of the equivalent circuit in FIG. 9;

FIG. 12 is a view of an embodiment, showing the construction of an grounded capacitive element which constitutes the circulator according to the present invention;

FIG. 13 is a view showing an embodiment of an essential portion of the lumped element circulator according to the present invention, the portion employing a spiral inductance; and

FIG. 14 is a view showing another embodiment of the essential portion of the lumped element circulator according to the present invention, the portion employing a beam lead capacitor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As previously stated, in the lumped element circulator, there exists the parasitic reactance component due to the reciprocal reactances of the parasitic reactance component due to the reactance present at the input end of each line conductor and the reactance between the line conductors. Therefore, the reciprocal reactances contained in nonreciprocal inductive elements for effecting the circulator operation will be first explained with reference to equivalent circuits of the lumped element circulator.

The eigen-impedances of the structure in FIG. 1 for in-phase, positive-rotating and negative-rotating excitations are set at Z Z, and Z respectively. The RF magnetic field within the ferrimagnetic substrate becomes almost zero for in-phase excitation, so that Z 0. In the case of positive-rotating or negative-rotating excitation, positive and negative circular rotating fields are generated within the ferrimagnetic substrate and in a plane orthogonally intersecting with the DC magnetic field. The respective effects can be expressed by the impedances of (imp. Ln), and (jam. Ln). These are components which contribute to the nonreciprocal operation of the circulator.

In contrast, that component of the RF magnetic field which is parallel to the DC magnetic field does not contribute to the nonreciprocal effect, but it acts as a mere reciprocal component. It becomes the parasitic reactance component. Although the influence of the reciprocal component is small in case where the line conductors are fully embedded in the ferrimagnetic substrate it is not negligible in case where the line conductors are exposed to the air as shown by way of example in FIG. 1. Lettingj w Lr be the impedance of the reciprocal component, Z and Z can be expressed as follows:

Z =jwLr +jmp. Ln

Here, p.+ and p. have the following relation with the component of the tensor permeability of the magnetic substance:

I F k The impedance matrix (Z) of the rotationally symmetrical circulator is generally given by the following equallOflI The voltages V V and V and currents 1,, I and 1 of the respective input terminals shown in FIG. 2, the impedance matrix has the following relation:

matrix (2) and the intrinsic impedances Z0. Z and Z 2 2 (Z l (1 2 01 (X) Z l/3 (2 a Z, a Z

where a exp 2/3 11).

Substituting Z, 0 and Equations (1) and (2) into Equations (7), (8) and (9) we obtain:

Accordingly, using Equations (3) and (4), the impedance matrix (Z) reduces to:

1 I 1 I 2 2 .2 l 1 1 J 2 2 {)wLn h VVVVVVVV '7 i i L l L a mwii'iivmilk' F5 T 2 In Equation (13 the first term of the right-hand side is the reciprocal component, and the second term is the component contributive to the nonreciprocal operation of the circulator. Where the reciprocal component is negligible, that is. where Lr 0, the impedance matrix (Z) is expressed by only the second term of the righthand side of Equation l 3). Then, the circulator can be constructed by connecting a capacitive element of appropriate value in parallel with each input terminal. Accordingly, it suffices that the first term in Equation (13) can be corrected. Now an inductive element (having an inductance Ls) is connected between the conductor plate on the back of the ferrimagnetic substrate and the outer conductor. Then, since all the currents flowing into the respective terminals pass through the element, the effect is equivalent to adding the following to the impedance matrix (Z) given by Equation (13):

1 1 l jmLs l 1 1 l l 1 Accordingly, if the value of the element is selected H0 that Ls N3 Lr, the sum between the abovementioned term and the first term of Equation (l3) becomes:

1 0 0 (Zr)=jwLr 0 l O (14) That is, only the component of non-diagonal parts of the impedance matrix leading to the reciprocal component is corrected.

The remaining parts in Equation 14) depend only on the currents flowing through the respective terminals. Therefore, in order to correct them, capacitive elements (having a capacitance of Cs) are connected in series with the respective input terminals. Then, the effect is equivalent to adding the following to Equation (14):

l l O j 0 l O wCS 0 0 1 If the value of the elements is selected so that mCs l/wLr, (Zr) 0. That is to say, the reciprocal reactance component indicated by the first term of Equation 13) can be corrected by connecting the capacitive elements in series with the respective input terminals and the inductive element between the conductor plate on the back of the ferrimagnetic substrate and the outer conductor.

Thus. the lumped element circulator according to the present invention takes the form shown in FIG. 4, when it is shown as an equivalent circuit. As seen in the figure, capacitive elements 51, 52 and 53 are connected to the respective input terminals, while an inductive element 54 is incorporated between the conductor plate and the outer conductor.

In FIG. 4, numerals 55-57 designate capacitive elements respectively corresponding to those 44-46 shown in FIG. 3.

As apparent from such an equivalent circuit, the lumped element circulator according to the present invention can, of course, be realized by employing, for example, known beam lead type capacitors as the capacitive elements and employing a coil as the inductive element and by connecting them in a conventional manner.

FIGS. a and 5b show an embodiment of the lumped element circulator which has been realized in such a way. As illustrated in FIG. 5a, beam lead type capacitors 51 52 and 53 are connected to the circulator in FIG. I by thermally bonding each capacitor on both sides of a groove formed at each input end. As in the sectional view of FIG. 5b, a coiled wire 54 is connected between a conductor plate 58 on the back of the ferrimagnetic substrate 31 and the outer conductor (ground in the figure).

As described above, in accordance with the present invention, the parasitic reactances not contributing to the nonreciprocal operation in the circulator of the lumped element substrate can be perfectly compensated.

The circulator can be rendered to have a wide band width in such a way that, as shown in FIG. 6, a series resonance circuit consisting of a capacitive element 61 and an inductive element 62 is connected to each input terminal of the lumped element circulator illustrated in FIG. 4.

An alternative measure is illustrated in FIG. 7. Herein. the capacitive elements 55, 56 and 57 connected to the respective input terminals and the inductive element 54 connected to the conductor plate on the back of the ferrimagnetic substrate are mutually connected and a series resonance circuit consisting of a capacitive element 71 and an inductive element 72 is connected between the common connection point and the outer conductor.

Similarly, to the case of FIGS. 5a and 5b, the circulators of the equivalent circuits in FIGS. 6 and 7 can respectively be realized.

As described above, the parasitic reactance caused by the inductive component acting as the mere reciprocal reactance can be compensated. Description will now be made of the case of respectively compensating the parasitic reactance due to the electrostatic coupling capacitance at the crossing parts between the line conductors and the parasitic reactance due to the series inductance present at the input end of eachline conductor.

The intrinsic impedances of the lumped element circulator shown in FIG. 1 and for the rotating excitation and the in-phase excitation are as shown by equivalent circuits in FIGS. 8a and 8b, respectively. In the figures, L, at 64 is the series parasitic inductance at the input terminal part, while C, at 65 is the parasitic capacitance attributable to the static coupling capacitance between the conductors. X, and X- at 63 are inductive reactances coupled between the conductor lines in the intrinsic impedances for thepositiveand negative-rotating excitations, respectively. As is well known, in order to construct a circulator operating at a low magnetic field, intrinsic admittances Y Y and Y for the in-phase, positive-rotating and negative-rotating excitations need satisfy the following conditions:

where Z, denotes the load resistance of the circulator. Equations (l5)-(l7) give the conditions concerning the circulator of the low magnetic field operation. In case of the high magnetic field operation, the suffixes of Y may be replaced. Accordingly, the following explanation will be made in the case of the low magnetic field operation only.

FIG. 9 is an equivalent circuit diagram showing a further embodiment of the lumped element circulator according to the present invention. At each input end port, a correcting inductive element L, is added to the parasitic inductance L, (the combined inductances are shown at 66 in the figure). A capacitive element 67 (having a capacitance C,) is added between an end of the inductances closer to the input end and the conductor plate on the back of the ferrimagnetic substrate. Further, a capacitive element 68 (having a capacitance Cu) is added between the conductor plate and the grounded conductor. Using the equivalent circuit in FIG. 9, the intrinsic admittances for the in-phase, positive-rotating and negative-rotating excitations are evaluated as follows:

1 (20) jcuC -ljX Here, ,u. and k denote the diagonal and non-diagonal parts ofthe tensor permeability, respectively. L and L indicate inductances which are determined by the geometries of the ferrimagnetic substrate and the line conductors.

By way of example, FIG. 10 illustrates a case where L, L 2.5 nH, C,,= 3.0 pF, the saturation magnetization M,,= 400 Gauss, the internal DC magnetic field H,

= 300 Oe, and the nonreciprocal filling factor lr 0.5.

The band characteristic varies in dEEeiiHeRfih'fiE value of (L, L and the value of C,,. The wide band characteristic shown in FIG. 10 is obtained by appropriately setting these values.

The lumped element circulator according to the present invention as depicted by the equivalent circuit in FIG. 9 can be realized as below. As the inductive element to be added to the input end of each line conductor, a narrow part whose length is shorter than a predetermined wavelength (for example, for a wavelength A, the narrow part is desirably shorter than approximately A/IO) is formed at the input end of each line conductor as is illustrated in FIG. 11. In the embodiment shown in FIG. 11 the line conductors are changed in shape as Herein, in order that the circuit can be realized, it is required that L L, O, that C, 0 and that C 0. When conditions for the requirements are evaluated from Equations (21 (23), the following is obtained:

FIG. 10 illustrates an example of calculation of the reverse direction loss of the lumped element circulator according to the present invention. In the calculation,

shown at 81, 81 and 81 to construct the narrow parts at the input ends. As the capacitive elements 67, the known beam read type capacitors, for example, are connected as shown at 82, 82' and 82". The capacitive element to be added between the conductor plate on the back of the substrate and the grounded conductor can be realized in such way that, as depicted in a sec' tional view of the circulator in FIG. 12, a dielectric substance layer 60 is interposed between the conductor plate 58 and the grounded conductor 59.

Further, a known spiral inductor, coiled wire or the like may be employed as the inductive element to be added to each input end, while the conventional read beam capacitor may be employed as the capacitive element 68.

FIG. 13 illustrates the case where the spiral inductor is connected to the input end of each line conductor. In the figure, the spiral inductor 97 is shown only for the conductor 11. The line conductors, to which the spiral inductors are connected in the illustrated manner, are arranged as shown in FIG. 1 and form the lumped element circulator.

FIG. 14 is a sectional view of the lumped element circulator in the case where the beam lead capacitor is used as the capacitive element for the connection between the conductor plate on the back of the substrate and the grounded conductor. In the figure, 98 indicates the beam lead capacitor which is connected between the conductor plate 58 on the back and ground.

What we claim is:

I. In a lumped element circulator including:

a ferrimagnetic substrate;

three line conductors arranged on a surface of said substrate with cross angles defined at with respect to one another and in a manner to be insulated from one another;

a first capacitive element connected between an input end of said each line conductor and an outer refinery; and J a conductor plate to which terminating ends of said respective line conductors are connected and which is provided on a back surface of said ferrimagnetic substrate;

a DC magnetic field being applied perpendicularly to the plane of said ferrimagnetic substrate;

the improvement comprising:

a first reactance element connected in series with said input end of said each line conductor; and

a second reactance element connected between said conductor plate and said outer conductor.

2. An improved circulator as defined in claim 1, wherein said first reactance element is composed of a second capacitive element, and said second reactance element is composed of a first inductive element.

3. An improved circulator as defined in claim 2, wherein said second capacitive element is a beam lead type capacitor.

4. The circulator as defined in claim 2, wherein said first inductive element is composed of a coiled wire.

5. An improved circulator as defined in claim 2, wherein a second inductive element and a third capacitive element are connected in series with said second capacitive element.

6. An improved circulator as defined in claim 1, wherein said first reactance element is composed of a first inductive element, and said second reactance element is composed of a second capacitive element.

7. An improved circulator as defined in claim 6, wherein said first inductive element is composed of a spiral inductor.

8. An improved circulator as defined in claim 6,

wherein said first inductive element is composed of a coiled wire.

9. An improved circulator as defined in claim 6, wherein said second capacitive element is composed of a beam lead capacitor.

10. An improved circulator as defined in claim 6, wherein said first inductive element is composed of a narrow part formed at said input end of said each line conductor.

11. An improved circulator as defined in claim 6, further comprising a third capacitive element connected between the end of said first inductive element opposite its connection with the end ofa respective line conductor and said conductor plate.

12. An improved circulator as defined in claim 11, wherein said third capacitive element comprises a beam lead capacitor.

13. An improved circulator as defined in claim l2,

wherein said first inductive element is composed of a narrow part formed at said input end of said each line conductor.

14. An improved circulator as defined in claim 13, wherein said second capacitive element includes a dielectric substance layer interposed between said conductor plate and said outer conductor.

15. In a lumped element circulator including:

a ferrimagnetic substrate;

three line conductors arranged on a surface of said substrate with cross angles defined at with respect to one another and in a manner to be insulated from one another;

a conductor plate to which terminating ends of said respective line conductors are connected and which is provided on a back surface of said ferrimagnetic substrate; and

a DC. magnetic field being applied perpendicularly to the plane of said ferrimagnetic substrate;

the improvement comprising:

a first inductive element coupled between said conductor plate and an outer conductor;

a first capacitive element connected in series with an input end of each line conductor;

a second capacitive element connected between said input end of each line conductor and said first inductive element; and

a second inductive element and a third capacitive element connected in series between the connection point of said second capacitive element and said first inductive element and said outer conductor.

16. In a lumped element circulator including:

a ferrimagnetic substrate;

three line conductors arranged on a surface of said substrate with cross angles defined at 120 with respect to one another and in a manner to be insulated from one another;

a conductor plate to which terminating ends of said respective line conductors are connected and which is provided on a back surface of said ferrimagnetic substrate; and

a DC. magnetic field being applied perpendicularly to the plane of said ferrimagnetic substrate; the improvement comprising:

a first inductive element connected in series with an input of each line conductor;

a first capacitive element coupled between said conductor plate and an outer conductor; and

a second capacitive element connected between the end of said first inductive element opposite its connection with the end of a respective line conductor and said conductor plate.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 836, 874 D d September 17, 1974 l f fl Minoru Maeda, Ichiro Ikushirna 7 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title page insert the following:

[30] Foreign Application Priority Data June 23, 1972 Japan. 62403/72 November 13, 1972 Japan 113001/72 Signed and sealed this 17th day of December 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. C; MARSHALL DANN Attesting Officer Commissioner of Patents 

1. In a lumped element circulator including: a ferrimagnetic substrate; three line conductors arranged on a surface of said substrate with cross angles defined at 120* with respect to one another and in a manner to be insulated from one another; a first capacitive element connected between an input end of said each line conductor and an outer conductor; and a conductor plate to which terminating ends of said respective line conductors are connected and which is provided on a back surface of said ferrimagnetic substrate; a DC magnetic field being applied perpendicularly to the plane of said ferrimagnetic substrate; the improvement comprising: a first reactance element connected in series with said input end of said each line conductor; and a second reactance element connected between said conductor plate and said outer conductor.
 2. An improved circulator as defined in claim 1, wherein said first reactance element is composed of a second capacitive element, and said second reactance element is composed of a first inductive element.
 3. An improved circulator as defined in claim 2, wherein said second capacitive element is a beam lead type capacitor.
 4. The circulator as defined in claim 2, wherein said first inductive element is composed of a coiled wire.
 5. An improved circulator as defined in claim 2, wherein a second inductive element and a third capacitive element are connected in series with said second capacitive element.
 6. An improved circulator as defined in claim 1, wherein said first reactance element is composed of a first inductive element, and said second reactance element is composed of a second capacitive element.
 7. An improved circulator as defined in claim 6, wherein said first inductive element is composed of a spiral inductor.
 8. An improved circulator as defined in claim 6, wherein said first inductive element is composed of a coiled wire.
 9. An improved circulator as defined in claim 6, wherein said second capacitive element is composed of a beam lead capacitor.
 10. An improved circulator as defined in claim 6, wherein said first inductive element is composed of a narrow part formed at said input end of said each line conductor.
 11. An improved circulator as defined in claim 6, further comprising a third capacitive element connected between the end of said first inductive element opposite its connection with the end of a respective line conductor and said conductor plate.
 12. An improved circulator as defined in claim 11, wherein said third capacitive element comprises a beam lead capacitor.
 13. An improved circulator as defined in claim 12, wherein said first inductive element is composed of a narrow part formed at said input end of said each line conductor.
 14. An improved circulator as defined in claim 13, wherein said second capacitive element includes a dielectric substance layer interposed between said conductor plate and said outer conductor.
 15. In a lumped element circulator including: a ferrimagnetic substrate; three line conductors arranged on a surface of said substrate with cross angles defined at 120* with respect to one another and in a manner to be insulated from one another; a conductor plate to which terminating ends of said respective line conductors are connected and which is provided on a back surface of said ferrimagnetic substrate; and a D.C. magnetic field being applied perpendicularly to the plane of said ferrimagnetic substrate; the improvement comprising: a first inductive element coupled between said conductor plate and an outer conductor; a first capacitive element connected in series with an input end of each line conductor; a second capacitive element connected between said input end of each line conductor and said first inductive element; and a second inductive element and a third capacitive element connected in series between the connection point of said second capacitive element and said first inductive element and said outer conductor.
 16. In a lumped element circulator including: a ferrimagnetic substrate; three line conductors arranged on a surface of said substrate with cross angles defined at 120* with respect to one another and in a manner to be insulated from one another; a conductor plate to which terminating ends of said respective line conductors are connected and which is provided on a back surface of said ferrimagnetic substrate; and a D.C. magnetic field being applied perpendicularly to the plane of said ferrimagnetic substrate; the improvement comprising: a first inductive element connected in series with an input of each line conductor; a first capacitive element coupled between said conductor plate and an outer conductor; and a second capacitive element connected between the end of said first inductive element opposite its connection with the end of a respective line conductor and said conductor plate. 